Optical surface monitoring and pillow positioning configuration for complex system's set-up

Abstract

Optical Surface Monitoring and Pillow Positioning Configuration for Complex System’s Set-Up: Aligning the patient’s target volume, isocenter and OARs with the linac’s isocenter can be done using certain immobilization device and imaging to adapt therapy if any variation of the tumor or patient’s body has occurred. In this investigation, a configuration of 10 pillows and Vision RT were employed to positioning the patient while it was checked by CBCT. The results show that for non-coplanar fields, Vision RT is accurate enough, with shifts less than 1º and 1mm. 4 pillows in a wedge under the head show an accurate position in the rotational axis (lessthan 1º) comparing with Vision RT and the off-set values given by the CBCT, although more pillows should be necessary for thorax and pelvis plans, since the differences between both methods are in average of 5 mm and 10º. Since the image registration was made manually, there are difference between 2 CBCTs of 6 mm and 5º in average in each plan, around the same magnitude than the difference between the two methods, so the differences might be due to the fact that Vision RT matches surfaces and CBCT matches the target volume, and because the manual image registration is involved with a human error